Unremarkable path involving kilometres in tortuous road (8)
I believe the answer is:
workaday
'unremarkable' is the definition.
('workaday' can be a synonym of 'unremarkable')
'path involving kilometres in tortuous road' is the wordplay.
'path' becomes 'way' (way is a kind of path**).
'involving' is an insertion indicator.
'kilometres' becomes 'k'.
'in' is an insertion indicator.
'tortuous' is an anagram indicator.
'road' with letters rearranged gives 'orad'.
'k' put into 'orad' is 'orkad'.
'way' placed around 'orkad' is 'WORKADAY'.
(Other definitions for workaday that I've seen before include "Mundane" , "Ordinary" , "Dull" , "Unexceptional" .)